1. Field of the Invention
The invention relates to a combustion chamber which has an improved air supply.
2. Discussion of Background
The combustion chambers of gas-turbine plants are supplied with liquid and/or gaseous fuel and atomization air via a number of burners. To this end, the burners are often arranged in a burner dome which closes off the space around the burners, the so-called plenum, to the outside. The plenum is arranged upstream of the combustion chamber and connected to the combustion-chamber wall. The air required for the combustion is delivered by the compressor of the gas-turbine plant. In the process, the main air flow is first of all used to cool the combustion-chamber wall and to this end is directed in cooling ducts on the outside on the combustion-chamber wall. The cooling ducts lead into the plenum. From there, the air preheated in the cooling ducts passes as combustion air via the burners into the combustion chamber and is finally burned together with the fuel used. In order to be able to ensure reliable burner operation, a defined flow structure must be imposed on the combustion air entering the burner dome.
With the use of newer combustion-chamber cooling techniques, the requisite cooling-air and combustion-air quantities differ markedly from one another in part. Since very large air quantities are desired for the combustion, an appropriate air quantity of the compressor air flow, in addition to the cooling air, is passed directly into the burner dome. So that this so-called bypass air can likewise be introduced into the plenum, suitable openings are formed in the burner dome, as shown, for example, by DE 195 16 798 A1.
A further solution for the addition of bypass air is disclosed by DE 195 23 094 A1, in which solution this secondary air flow is introduced into the main air flow (cooling air) via at least one injector system located at the transition to the plenum. Given good mixing of both air flows, a small pressure loss can thereby be realized.
In accordance with the thermal design of the gas turbine and the fuel used, however, the air requirement for the combustion in the combustion chamber and for the cooling of the combustion chamber may vary considerably. It is therefore necessary for the bypass air quantity to be variable. Despite a changed mass flow of the bypass air, however, the flow conditions in the burner dome must not be disturbed. Otherwise, i.e. under unfavorable inflow conditions of the bypass air, vortices, backflow zones and other phenomena of this type, which may have an adverse effect on the main air flow and its stability, are produced.